Investigation of electrochemical properties of NMC/Graphene Cathode active materials coated with Cerium(IV) Fluoride and Lithium Fluoride

Lithium-ion batteries are commonly used as power source systems for computers, cell phones, and electric vehicles (EVs). In recent years, Li(Ni0.33Mn0.33Co0.33)O2 (NMC) has been more preferred cathode active material due to its properties of high reversible capacity, high power, more safety, low environmental impact and low cost. Besides these good qualities, poor rate capabilities, poor cycle life, thermal instability and cation mixing are some disadvantages experienced by this cathode. There are many researches focusing on ion doping, surface coating or forming composites containing the conductive materials and cathode active materials to solve these problems in the literature. In the scope of this study, the cathode active materials of Li1.1(Ni0.33Mn0.33Co0.33)O2 and Li1.1(Ni0.33Mn0.33Co0.33-xMx)O2 (x=0.05 Fe and Cu) were synthesized with solid state synthesis method. The effects of conductive material N-doped graphene oxide (N-GO) and surface modification with cerium(IV) fluoride (CeF4) and lithium fluoride (LiF) on the electrochemical performances of these synthesized materials were investigated. After the synthesis processes were completed, scanning electron microscope (SEM), X-ray diffraction (XRD) and energy dispersive X-ray spectroscopy (EDS) were utilized for material characterization of cathode active materials. Moreover, for electrochemical characterizations, tests were carried out to evaluate the initial discharge capacity, cycling and rate capability performances in the battery testing system. Key Words : Lithium-ion Batteries, Metal Doping, Cerium(IV) Fluoride, Lithium Fluoride, Surface Modification